o prompt: fix readline line editing with ANSI prompt

Wrap bold escape sequences in \001/\002 markers so readline
correctly tracks cursor position. Fixes Ctrl+U, Ctrl+W, and
other readline kill commands after typing several characters.

data/scripts/o

@@ -260,7 +260,7 @@ cmd_prompt() {
     while true; do
         local prompt_str
         if [[ -z "$buf" ]]; then
-            prompt_str=$'\033[1m>\033[0m '
+            prompt_str=$'\001\033[1m\002>\001\033[0m\002 '
         else
             prompt_str="  "
         fi